1. Field of Invention
The present invention is directed to semiconductor light emitting devices including heavily doped current spreading layers.
2. Description of Related Art
Semiconductor light emitting devices such as light emitting diodes (LEDs) are among the most efficient light sources currently available. Material systems currently of interest in the manufacture of high brightness LEDs capable of operation across the visible spectrum include group III–V semiconductors, particularly binary, ternary, and quaternary alloys of gallium, aluminum, indium, and nitrogen, also referred to as III-nitride materials; and binary, ternary, and quaternary alloys of gallium, aluminum, indium, and phosphorus, also referred to as III-phosphide materials. Such devices typically have a light emitting or active region sandwiched between a p-doped region and an n-doped region. Often III-nitride devices are epitaxially grown on sapphire, silicon carbide, or III-nitride substrates and III-phosphide devices are epitaxially grown on gallium arsenide by metal organic chemical vapor deposition (MOCVD) molecular beam epitaxy (MBE) or other epitaxial techniques.
Devices grown on a conductive substrate often have the contacts formed on opposite sides of the device. Alternatively, on devices grown on poorly conducting substrates, or for optical or electrical reasons, the device may be etched to expose portions of both the n- and p-type regions on the same side of the device. The contacts are then formed on the exposed regions. If the contacts are reflective and light is extracted from the side of the device opposite the contacts, the device is referred to as a flip chip. Since at least one of the contacts on a flip chip device does not directly overlie the active region, if current is not efficiently spread through the p- and n-type regions, device performance may suffer.